1. Field of the Invention
This invention relates generally to acoustical hearing devices. More particularly, this invention relates to hearing protective devices comprising a foam and at least one mechanically bonded component during the manufacturing process.
2. Brief Description of the Prior Art
The use of hearing protection and noise attenuating devices are well known, and various types of devices are available for this purpose. Such devices include, but are not limited to, earmuffs, semi-aural devices, and earplugs. Foam components are well-known for use with these devices, providing both sound attenuation and enhanced comfort for the wearer.
Earplugs are generally preferred for continuous use over longer periods of time. Slow recovery foam earplugs such as those disclosed in U.S. Reissue No. 29,487 are not only comfortable, but have also been shown to deliver high in-field noise protection at all frequencies. U.S. Pat. No. 5,203,352 to Gardner, Jr. also discloses a hearing protective earplug comprising a polymeric foam.
With respect to all three types of devices, the sound-attenuating (acoustical) component has been made both of flexible, rubber-like materials, and of foam. For earplugs and semi-aural devices, the rubber-like materials are advantageous in allowing direct insertion into the wearer's ear, but are sometimes uncomfortable over long periods of use. Foam earplugs and pods provide enhanced comfort, but require "rolling-down" before insertion. In addition, manufacture of foam components requires the presence of a vent in the mold for entrapped gases to escape, which often results in foam overflowing the vent ("flash"). This flash is wasteful, and must be cleaned off the molds after each molding. Cleaning the molds can be a long, tedious procedure which adds significantly to manufacturing time.
A foam earplug or pod with a stem insert can provide both the ease of insertion of rubberlike earplugs, with the comfort of foam earplugs and pods. In fact, a number of patents have been directed to earplugs having tips or flanges with a relatively stiff stem used to insert and remove the earplug. One especially useful earplug, shown in FIG. 1, is described in U.S. Pat. No. 5,188,123 to Gardner, herein incorporated by reference. This earplug 2 comprises a circular or ovoid resilient polymeric foam body 4 having a rounded nose end 6. An elongate stem 8 is axially embedded in main body element 4 and extends rearwardly and axially therefrom. The earplug may be used in a push-in or roll-down insertion mode.
While suitable for certain purposes, this prior art earplug requires an additional manufacturing step to secure the stem in the foam body, i.e., a gluing step. Furthermore, the bond is sometimes not as permanent as is desirable. In addition, if the stem is too hard it may be considered unsafe to the user, the general concern being that potential injury could result should the hearing protector become impacted. On the other hand, if the stem is too soft, it tends to buckle upon insertion, limiting the fit of the earplug and reducing the potential usefulness of the stem.
One attempted solution has been to provide an insertion tool, consisting of a stiff tube that fits over the soft stem. However, the use of an additional part increases the cost of manufacture and may be inconvenient for the user. Another attempted solution has been to use a relatively stiff material, but reduce the diameter of the stem. However, this solution results in decreased comfort for the wearer, apparently due to the increased pressure that results from use of a smaller diameter stem.
Still another exemplary prior art ear plug is disclosed in U.S. Pat. No. 5,799,658 to Falco which is assigned to the assignee hereof, all of the contents of which are incorporated herein by reference. Referring to prior art FIGS. 2 and 3, this prior art earplug or semi-aural device pod 10 comprises a foam 12 mechanically bonded to a porous component 14 having a handle portion 16 and an embedded portion 18 with a tip 20. "Embedded portion" refers here to that part of the porous insert which is surrounded by, and mechanically bonded to, the foam component The earplug may be of any configuration, such as circular or ovoid, with the preferred configuration having a flange 13. During manufacture, porous component 14 is placed in a mold and a foam is formed within the mold such that foam penetrates the embedded portion 18 of porous component 14, thereby forming a mechanical bond between the foam and the porous component.
One problem with the just discussed prior art ear plug is that the sources for porous component 14 are quite limited. For this and other reasons, although the above prior art ear plugs have been satisfactory for their intended purpose, there remains a need for stemmed foam ear plugs that are safe for the wearer, yet convenient and comfortable to use and which does not require a separate gluing step to adhere to the part.